Transition metal chromium

Not all ligands use just two electrons to bond to transition metals Chromium has the electron configuration [Ar]4s 3rf (6 valence electrons) and needs 12 more to satisfy the 18 electron rule In the compound (benzene)tricarbonylchromium 6 of these 12 are the tt elec Irons of the benzene ring the remammg 6 are from the three carbonyl ligands... 

Cr03 As a transition metal, chromium forms more than one stable cation. Name the metal first, using a Roman numeral to designate chromium s charge. Each of the three oxide anions has a -2 charge. To maintain net charge neutrality, Cr must be +6, so the name of the compound is chromium(VI) oxide. 

Acetic anhydride, Organic materials, Transition metals Hikita, T. et al., J. Chem. Soc. Japan, Ind. Chem. Sect., 1951, 54, 253-255 The stability ranges of mixtures of the acid, anhydride and organic materials (ethanol, gelatine) used in electropolishing were studied. Presence of transition metals (chromium, iron, nickel) increases the possibility of explosion. (This is why such mixtures must not be stored after use for etching metals.)... 

Abstract This chapter focuses on well-defined metal complexes that serve as homogeneous catalysts for the production of polycarbonates from epoxides or oxetanes and carbon dioxide. Emphasis is placed on the use of salen metal complexes, mainly derived from the transition metals chromium and cobalt, in the presence of onium salts as catalysts for the coupling of carbon dioxide with these cyclic ethers. Special considerations are given to the mechanistic pathways involved in these processes for the production of these important polymeric materials. 

Some metals, such as the transition metals chromium and titanium, are prepared from their oxides using this type of competition reaction. 

These common uses only hint at all the things that transition metals can do. The copper penny, for instance, is mostly made of zinc, another transition metal. Chromium provides the shiny, mirror-like metal coating on chrome car bumpers, but is also added to some lasers to make their light shine red. Nickel and chromium combine in an alloy that can be coiled into the wires that heat toasters and hair dryers. Titanium dioxide is a very white reflective compound used in toothpaste and paints. The transition metal cadmium is used in brilliant and permanent colors such as cadmium yellow, red, and orange. Artists have used cadmium-based paints for hundreds of years, and manufacturers used the colors more recently in plastic products. However, the colors are rarely used now that scientists have discovered that cadmium pollution can cause cancer and other health problems. 

Most of the metallic oxidants which have been used for the oxidation of ethers have been based on oxides of the transition metals chromium, manganese and ruthenium, the latter being of greatest synthetic importance. The first reported example of the application of ruthoiium tetroxide in the oxidation of ethers tqipeared over 30 years ago in 1958, although an indication of its reactivity towards ethers had been obt ed some years before. In a systematic study which revealed the powerful oxidizing properties of the reagent, Berkowitz and Rylander demonstrated the quantitative conversion of tetrahydrofuran and R-butyl ether into y-butyrolactone and butyl butyrate, respectively. Significantly, no overoxidation was observed. Apart f m an unsuccessful attempt to oxidize ethylene oxide, no fitter attempts were made by the authors to examine further the scope of this novel transformation. In a series of subsequent publications and a patent, Wolf and his coworkers went on to exploit the reaction in the preparation of aldosterone and relr steroids (equation 1). 

Carbonyl Complexes of the Transition Metals Chromium Inorganic Coordination Chemistry Dinuclear... 

For the insoluble transition metals chromium, cobalt, and nickel, McLennan s (2001b) recent evaluation suggests approximate factor of 2 increases in average upper crustal values over those of Taylor and McLennan (1985). Taylor and McLennan s (1985) values were taken from a variety of sources (see Table 1 of Taylor and McLennan, 1981) and are similar to the Canadian Shield averages, which appear to represent a more felsic upper-crust composition, as discussed above. Even after eliminating these lower values, 30-40% variation exists for chromium, cobalt, and nickel between different estimates (Table 2 and Figure 3), and the upper cmstal concentrations of these elements remains poorly constrained relative to REE. 

We shall illustrate the content of the present section with the examples of the 3d band transition metal chromium [2.13] in its bcc paramagnetic phase and the 6s6p band metal thallium [2.6] in its hep phase. 

Hughbanks, T., Rosenthal, G. Corbett, J. D. (1988). Encapsulation of the Transition Metals Chromium Through Cobalt in Zirconium Cluster Iodides, J. Am. Chem. Soc. 110, 1511-1516. 

In this chapter we also briefly considered some chemistry of three of the common transition metals chromium, iron, and copper. 

Many of the preferred reagents for the oxidation of primary alcohols to aldehydes (secondary alcohols to ketones) contain the transition metal chromium in its highest oxidation state, VI. Upon reaction with an alcohol, the yellow-orange chromium(VI) species is reduced to the blue-green chromium(III) state. Normally the reaction is carried out in aqueous acid solution using the sodium dichromate salt, Na2Cr207, or the oxide, CrOs. A typical reaction is shown here ... 

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